In addition to those factors, I think a big part of it is that the PlayStation landscape and CAG demographics have changed in a way that reduces demand for gamesharing.
I was a regular in the old thread back in about 2011-2012. Back then, PSN had barely any decent discounts, PS+'s library was still small, and GamePass didn't exist, so digital console gaming could be pretty expensive unless you gameshared. You can still save a lot gamesharing new releases nowadays, but once a game's been out for a few months and its price starts dropping, the incentive to jump through the GS hoops isn't there as much. I used to browse here for random smaller/older games to try out too, but now PS+ offers hundreds of those to try out instantly, so I suppose that draw isn't as strong anymore.
And then the shift in demographics. Younger generations aren't using message boards like this one much anymore, so I think it's fair to say CAG's userbase is largely 30+ now, many settled into careers, raising families, etc. and finding we have more money for games than time to play them (instead of the other way around). Alas, once a CAG always a CAG, so we keep coming back to make sure we don't miss out on the next great deal..